| 摘要 |
PURPOSE:To enable compensation for a change of gas density in a counter tube by the use of a simple mechanism by installing a means in which a temperature of a liquid container is kept identical with that of a proportional counter tube. CONSTITUTION:Water is housed in a container 7 with a cross-sectional area Sb, and also water is housed in a thin tube 6 with the cross sectional area Sa having its one end opened on a side of an atmospheric pressure side. The atmospheric pressure is expressed in Hat. One barometric pressure is applied to both an inside of the container 7 and a water surface (a) in the thin tube 6. When a valve 9 is closed at a temperature of T deg.K so as to make the container 7 airtight, a pressure of the water surface (a) is kept one barometric pressure and then a height of a gas column in the container 7 is made l. Dimensions of respective portions of the container are determined so that the temperature in the container 7 is identical with that of the gas flow propor tional counter tube PC1 and a relation (Sb/Sa)/{(Hat /l)+(Sb/Sa)+1} 1 is satisfied. Resultingly, the pressure inside the PC1 is increased to the maximum where expansion of the gas does not automatically occur, so that the gas density inside the counter tube is kept constant.
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